Rupture process of the 2021 M7.4 Maduo earthquake and implication for deformation mode of the Songpan-Ganzi terrane in Tibetan Plateau

Abstract

Significance The Songpan-Ganzi terrane lies in the central-east of the Tibetan Plateau, which was considered a stable block in some tectonic models. Its deformation mode is of crucial importance for understanding the evolutionary history and seismic hazard of the plateau. The recent Maduo earthquake occurred inside the terrane. We resolve a bilateral rupture process with distinct super- and subshear rupture modes for this event. We also find that pervasive folding structures that are aligned by shear deformation in the current Songpan-Ganzi terrane are responsible for the seismic wave anisotropy and shear strain orientation in its upper crust. Its deformation mode can be classified as distributed simple shear, which receives shear loads from side walls and produces internal earthquakes.

Simultaneous Rupture Propagation Through Fault Bifurcation of the 2021 Mw7.4 Maduo Earthquake

“…The rupture speed of the Maduo earthquake was quite stable around 2.5 km/s, which is in contrast with supershear rupture speed derived from the other BP analysis (Yue et al., 2022; Zhang et al., 2022). The primarily reason for this discrepancy could be that we applied travel time path calibrations (see more details in Zeng et al.…”

“…Earlier reports of the earthquake show that this was a bilateral rupture, which propagated ∼80 km to both sides of the epicenter (He et al., 2022; Ren et al., 2022; S. Wang, Song, et al., 2022). While (Chen et al., 2022) d erived a stable rupture speed of ∼2.5 km/s for the entire rupture, (Zhang et al., 2022) and (Lyu et al., 2022; Yue et al., 2022) reported a supershear speed for rupture toward the east. Recently, (Li et al., 2022) also reported asymmetric rupture velocities for the earthquake with a holistic approach.…”

“…Wang, Song, et al, 2022). While (Chen et al, 2022) d erived a stable rupture speed of ∼2.5 km/s for the entire rupture, (Zhang et al, 2022) and (Lyu et al, 2022;Yue et al, 2022) reported a supershear speed for rupture toward the east. Recently, also reported asymmetric rupture velocities for the earthquake with a holistic approach.…”

Earthquake Cycle Deformation Associated With the 2021 MW 7.4 Maduo (Eastern Tibet) Earthquake: An Intrablock Rupture Event on a Slow‐Slipping Fault From Sentinel‐1 InSAR and Teleseismic Data

“…Observations of potential supershear rupture speeds, as reported by Q. Li, Wan, et al (2022), W. Wang, He, et al (2022), Yue et al (2022), and X. Zhang, Feng, et al (2022), would support the suggestion that this is indeed a well-developed, structurally-mature fault, with fairly low slip-to-length ratio of the rupture (α = 5-10 × 10 −5 ) (e.g., Manighetti et al, 2007).…”

“…Both play an important role in accommodating the eastward extrusion of the Plateau. The slip rate of the KF decreases gradually from the Tuosuo Lake segment toward the eastern end (Diao et al., 2019) while the shear motion increases along the Ganzi‐Yushu‐Xianshuihe Fault (Yue et al., 2022), suggesting a possible tectonic role of the BHB in transmitting shear motion and strain partitioning through a series of sub‐parallel secondary faults in the interior (e.g., the Jiangcuo Fault, the Jiuzhi Fault, the Dari Fault, the Bayan Har Shan Main Peak Fault, etc.). The deformation along the KF may represent a diffuse tectonic block boundary, which accommodates differential motion between the BHB and the Qaidam Block in the north.…”